Transubstantiation is a very sensible and coherent way of expressing Roman Catholic eucharistic doctrine - or at least it was in about 1250. The classic formulation, in Thomas Aquinas, explains that in the mass the essence or substance of the bread and wine is genuinely changed into the essence of the body of Christ. The bread and wine still appear to be bread and wine to us, because their accidents are unchanged; that is to say, all that appears to the senses is still exactly as it was before. Faith is required here: not to make the change (this is thought to be objective), or to receive the changed host (this is done, whether to judgement or salvation, by everyone who partakes), but to perceive the host as genuinely being the body of Christ, since the senses won't help.
As I said, this all makes sense in 1250. Aquinas leans heavily on Aristotelian philosophy for the language of substance and accidents. For Aristotle, accidents or properties of things reside in their substances. The substance is the thing proper, and the accidents are, if you like, the presenting face. Of course, for Aristotle these things couldn't be separated. The idea that you could have a table that presented as a chair whilst remaining a table would have seemed bizarre to him. Aquinas would appeal to miracle here, again not unreasonably.
Now, there are all sorts of reasons not to follow Roman eucharistic theory at this point. The general thrust is wrong. But granted the basic direction of Roman Catholic theology, this made sense. Unfortunately, because at the Counter-Reformation the Catholic Church rather painted itself into a corner in terms of doctrinal change and the impossibility thereof, this is still the way the mass is explained today. And it makes no sense. Nobody believes in substances and accidents in this way anymore; nor should they. It is certainly not inconceivable that the doctrine of the mass could be re-expressed in a way which kept its essentials intact without relying on an obsolete philosophy - but Roman Catholicism has closed that path to itself 500 years ago. It's stuck with Aquinas, and therefore with Aristotle.
The reason I mention all this is because there is always a danger that Evangelicals, who are in theory open to their doctrine being continually reformed by the word of God, actually fall into the trap of holding on to formulations that no longer make sense, and in so doing losing the heart of the doctrine they're trying to defend. As an example, I was reading someone recently who, when challenged that the evangelical doctrine of inerrancy is a species of philosophical foundationalism, simply gave the verbal equivalent of a shrug - we are apparently committed to epistemological foundationalism. That would be an error. Foundationalism has, in my view rightly, been found wanting philosophically. And if our doctrine really springs from Scripture, we'd hardly want to wed ourselves completely to a philosophical doctrine that emerged with the Enlightenment! Surely we can express our commitment to the authority of Scripture in a new way - without losing it? Because my worry is that we will surely lose it - or at least, lose adherence to it - if we continue to express it in terms of an obsolete philosophy.
This is not about compromising with the spirit of the age. It's about recognising that we have always used the language and concepts of the day to express what we think we're hearing in Scripture. That is both inevitable and right - how else would we communicate today? But yesterday's formulations must be open to re-expression if we're to make sure that it is God's revelation attested in Scripture that is driving our doctrine, and to avoid getting stuck in philosophical cul-de-sacs.